There are a number of cardiovascular diseases that are characterized by weakness of supportive connective tissue, examples of which are cystic median degeneration of the aorta, dissecting aortic aneurysm, the syndrome of 'click murmur' (floppy) of the mitral valve, Marfan's syndrome and aneurysms of the membranous septum. Currently there is no satisfactory medical means of treatment for patients with these diseases. To date we have learned that propranolol at a dose that blocks beta receptors and reduces the pulse rate, blood pressure and the dp/dt of the rise in the pulse pressure curve decreases the tensile strength of the aorta of immature male and female turkeys. This propranolol-induced change in the mechanical properties of the aorta may be due to the decrease in the amount of chemically determined elastin and in the crosslinking density of collagen. The effects of propranolol on the scleroproteins of the aorta are reversed when propranolol is combined with an anabolic steroid, methandrostenolone. The methandrostenolone plus propranolol regimen increased the amounts of elastin and collagen in the aorta and the crosslinking density of collagen. The effect on elastin crosslinking is currently under study. These initial results were obtained on immature birds. Plans for the second year include studies of the effect of propranolol alone and in combination with an anabolic steroid on aortic scleroprotein of adult birds. Even at this early stage of the research, the results clearly indicate that pharmacologic agents can significantly affect the viscoelastic and biochemical properties of the aortic tissue. We are confident that drug combinations will emerge from these studies that will provide a therapeutic regimen for patients with structural weaknesses in cardiovascular tissue. BIBLIOGRAPHIC REFERENCE: Paff, G.H. and R.J. Boucek, Conal contribution to the electrocardiogram of chick embryo hearts. Anat. Record 182:169-174, 1975.